C150319 Feasibility Study - Laserfiche WebLink

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this pipeline along Broadway could result in a hazard to both motorists and pedestrians who use this corridor. Projects 3 and 4 could be deferred in definitely, resulting in maintenance of current ditch operations, operations and maintenance ex penditures, and water delivery reliability. Alternative 2 and Cost Opinions Alternative 2 – Project 1. Replace Diversion Headgate . Alternative 2 would require removal of the existing gate and replacement with a new 8-foot by 14-foot radial gate, which would be placed into the footprint of the exis ting headworks structure. This alternative would also require replacement of the existing hoist and actuat or, which are currently serviceable, due to incompatibilities with the new gate. Alternative 2 at the headgate was rejected in favor of Alternative 3 because the majority of the gate structure is in adequate condition and the lo wer quarter-to-third of the gate can be repaired more affordably than providing a new radial gate. Alternative 2 – Project 2. Replacement of Existing pipeline along Broadway . Alternative 2 would replace the existing, failed corrugated metal pi peline with a 36-inch diameter polyethylene pipeline (PE) and would replace the entire failed segment along Broadway. As discussed in the project introduction, there is currently not adequate cover along this segment to install a PE pipeline with adequate cover, so an inverted sip hon would be constructed to allow the pipe invert to be lowered. Additionally, Fisher would work with the Colorado Department of Transportation (CDOT) to allow the importation of additional f ill to raise the Broadway shoulder area to provide an additional margin of safety. Alternative 2 was rejected because providing a siphon in this area will increase the potential to trap debris and sediment, potentially increasing the maintenance costs for th is reach. Further, Fisher ditch is uncertain that sufficient cover can be obtained, depending on the outcome of the discussion with CDOT. Finally, Fisher believes that Alternative 3, while initially more expensive, will provide a longer-term solution to the Broadway pipeline problem. Alternative 2 – Project 3. Provide a sand-out structure downstream of Clear Creek diversion. Alternative 2 would repair an existing, but abandoned, spillway structure to serve at the sand-out. The structure is located in the upper canal re ach, approximately 1,000 feet downstream of the headgate and downstream of the measurement flume. Repair of this structure would include replacement of the spillway structure, including addition of a new slide gate, installation of a new check structure in the canal, and rehabilitation of the outlet channel including tree removal. Alternative 2 was rejected for several reasons: 1. Rehabilitation of the spillway is anticipated to be more expensive than constructing a new outlet structure. 2. The existing spillway is located too far do wn the ditch to serve its intended purpose. 3. The spillway is located below the ditch measurement flume and could complicate preparation of diversion records for the ditch while the sand-out is in use. 4. Tree removal along the outlet would likely be controversial to park users. Alternative 2 – Project 4. Ditch piping upstream of Federal Boulevard. Fisher has examined a number of alternatives to address the dumping issu e in this reach of the ditch, including meeting with the mobile home park management, constructing a fence along the mobile home park boundary, and removing the debris as it is dumped. Fisher would prefer that the mobile home park (with Fisher participation) install a more substantial fence at the mobile home park boundary to prevent dumping. While this alternative could address the problem in a less expensive and more effective manner, the mobile home park management has been unwilling to maintain the existing fencing in adequate repair to prevent dum ping or enforce a no dumping policy with its residents. As such, Alternative 2 was rejected an ineffective in solving the issue. Cost opinions for each project considered under Alternative 2 are summarized in Table 5. 8